Optical glass

ABSTRACT

THIS INVENTION RELATES TO THE OPTICAL GLASS OF HIGH REFRACTION AND LOW DISPERSION HAVING A BASIC COMPOSITION IN THE RANGE OF B2O3 28-42%, Y2O3 2-25%, LA2O3 5-55%, THO2 2-45% OF WEIGHT RATIO. IN THE ATTACHED DRAWINGS, FIGS. 1, 2,3,4 AND 5 ARE TRIANGULAR DIAGRAMS SHOWING THE STABLE REGION OF GLASS FORMATION IN THE COMPOSITION   B2O3-Y2O3-LA2O3-THO2   FOUR COMPONENT SERIES. FIGS. 6,7,8 AND 9 ARE TRIANGULAR DIAGRAMS SHOWING THE STABLE REGION OF GLASS FORMATION IN THE COMPOSITION RATIOS OF THE B2O3-Y2O3-LA2O3-THO2-BAO FIVE COMPONENT SERIES. FIG. 10 IS AN ND-VD DIAGRAM SHOWING THE OPTICAL VALUE OF SOME EXAMPLES IN THE TABLES.

June 13, 1972 ICHIZO SUZUKI ETA!- 3,669,696

omen. GLASS Filed July 9, 1969 5 Sheets-Sheet-I Fig. 1y

F g 50 B203 300% June 13, 1972 ICHIZO SUZUKI E 3,669,695

OPTICAL GLASS Filed July 9, 1969 5 Sheets-Sheet? Fig/w 3- Fig, 4-

I June 13, 1972 ICHIZOVSUZUKI ETAL 3,6

OPTICAL GLASS Filed July 9, 1969 Sneaks-Sheets Fig- 5-' 10 2o Y L612 03 Y203 June 13; 1972 ICHIZO SUZUKI ETAL 3,669,696

OPTICAL GLASS Filed July 9, 1969 5 Sheets-Sheet;

ThOz

iy/ N 16 40 B203 38.0% Ba06% IIA'A June 13, 1972 ICHIZO SUZUKI E L 3,659,696

OPTICAL GLASS Filed July 9, 1969 5 Shee'Es-Sheet S B203 38.0% BaO 6% 23 30 40 50 53 Laz O3 Y2 03 x A lass of the present, invention. q9- A glass of G.w. Morey'spatent. A glass of w-fieffckens atent.

United States Patent 3,669,696 OPTICAL GLASS Ichizo Suzuki, Sagamihara-shi, Hideo Yasui, Tokyo, and Kazuhiko Nanba, Sagamihara-shi, Japan, assignors to Kabushiki Kaisha Ohara Kogaku Garasu Seizosho, Sagamihara-shi, Kanagawa-ken, Japan Filed July 9,1969, Ser. No. 840,382 Claims priority, application Japan, Sept. 16, 1968, 43/ 67,808 Int. Cl. C03c 3/00, 3/14, 3/30 US. Cl. 10647 Q 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the optical glass of high refraction and low dispersion having a basic composition in the range of B 0 2842% Y O 225%, La O 55% ThO 2-45% of weight ratio. In the attached drawings, FIGS. 1, 2, 3, 4 and 5 are triangular diagrams showing the stable region of glass formation in the composition B203'Y203'L3-2O3'Th02 four component series. FIGS. 6-, 7, 8 and 9 are triangular diagrams showing the stable region of glass formation in the composition ratios of the B O -Y O'3-La O' -ThO -BaO five component series. FIG. 10 is an Nd-vd diagram showing the optical value of some examples in the tables.

The present invention relates to optical glass having high refraction and low dispersion and particularly to a glass having the four component base,

The inventors discovered the glassforming region of B O -Y 'O -La O -ThO four component glass wherein B 0 is present in amounts of 28%, 30%, 34%, 38% and 41% in weight respectively (same hereinafter), and have studied the optical property and tendency of devitrification thereof. As the result, it has been found that this four component glass series can produce glass having a very advantageous optical value, i.e. the glass has a low dispersion and resistivity to devitrification which is very great compared with known glass. In the glass series having the four components, B O -Y O -La O -ThO the glassformation regions in case of glass containing 2841% of B 0 are shown in FIGS. 1-5; they occupy a fairly large domain, when B 0 is present in amounts of 28%, 30% and 34% and it decreases considerably at a B 0 content of 38% of B 0 and is limited to the side having greater content of La O at a B 0 content of 41% of B 0 Now, there is no distinct scale defining glassformation to determine whether a composition is glassified or not. For example, when a few grams of glass is melted, and cooled rapidly from the molten state and is then in a glassy state, it can be said that it is glassified; hitherto, when a glassforming region is to be determined this is about the scale of melting which has been carried out.

The object of the present invention is to obtain stable glass by manufacturing it on an industrial scale, for this reason the usual scale of melting a few grams is enlarged to 100 grams in the method for determining the glassforming range, and the enlarged batch of glass is melted in a platinum pot at 1300 C.1400 C., the mixture is taken out of the pot in the molten state and cooled as is. The composition with no appearance of devitrification on the glass surface or in the glass is said to be glassified and the glassforming region has been determined.

The stability of B O -Y O -La O -ThO four component glass can be recognized from the extent of the glassforming region in compositions containing 28%, 30% and 34% of ice B 0 but the inventors of this invention have carried out comparative tests in order to certify the fact that the glass of four components of the present invention is more stable as compared with the three components series of glass as follows.

Namely, in the glassforming region at a content of B 0 38% as shown in FIG. 4, three kinds of glass designated A, B and C are tested and compared: glass not containing Y O having the composition B 0 38%, La O 52%, ThO 10%; as composition A a glass having the composition: B 0 38%, La O 47%, ThO 10%, Y O 5% as composition B; and a glass having the composition B 0 38%, La O 52%, Th0 5%, Y O 5% as composition C. To perform a comparison test of devitrification tendency, each composition has been subjected to the steps of lowering the temperature to 1200 C. after melting, then retaining for fifteen minutes at 1200 C., and lowering the temperature at uniform speed for one hour and fifteen minutes, and then was taken out of the furnace and was observed. Glass A not containing Y O and composed of B 0 38%, La O 52%, ThO 10% crystallized perfectly to the inner part. No crystal appeared either on the surface or inner part of the glass B composed of B 0 38%, U1 0, 47%, Th0 10%, Y O 5%. In glass C composed of B 0 38%, La O 52%, ThO 5%, Y O 5%, only its surface layer was crystallized but the results thereof were good compared with the glass A not containing Y203.

As the examples of the four component series, glass, the glass composition in weight percentage and the optical constant Nd, vd are shown in the Table 1 as follows:

TABLE 1 B203 LazOa Th0; YgOa Nd 144d Sample No.:

1 2s 17 40 15 1.7882 61.8 28 32 30 10 1.7915 51.5 28 22 30 20 1.7881 51.8 30 20 45 5 1.7750 52.3 30 5 40 25 1.7712 52.4 30 30 25 15 1.7786 52.1 30 15 30 25 1.7751 52.4 30 40 25 5 1.7815 51.9 34 31 30 5 1.7554 63.6 34 16 25 25 1.7500 53.4 34 1 20 15 1.7550 53.3 34 45 15 5 1.7512 53.0 34 41 10 15 1.7501 53.1 38 47 10 5 1.7394 54.0 as 32 10 20 1.7340 54.2 38 52 5 5 1.7423 53.9 as 37 5 20 1.7387 54.2

In this optical field, there are widely known glasses as disclosed, for example, in US. Pat. No. Re. 21,175 by G. W. Morey and German Pat. No. 1,054,209 (U.S. Pat. No. 3,082,101, Japanese pat. publication No. 11,761/ 1968) by W. Geifcken et al. In FIG. 10 glass N, T having an extremely low dispersion, disclosed by Morey is shown by a full line and the glass II 17, II 1, IV 4 having an extremely low dispersion, disclosed by Geficken et al. is shown by a broken line. Some examples of the glass according to the present invention in the table are shown by the marks x.

Referring to the optical values of glass composed of 30% and 28% B 0 clearly it has a lower dispersion as compared with said former two patents above Nd 1.77, and shows that it is a glass in a new field. Referring to the glass composed of more than 34% of B 0 in optical value, it has nearly the same advantage as compared with glass of the B O -La- O -ThO series disclosed by Gefl'cken et al.

Also, there is a US. Pat. No. 3,193,400 (Japanese Pat. No. 418,705) of Geficken disclosing a glass containing Y O and which shows the glassforming region of the three components series of B O -La O -Y a glass having the optical constant of Nd=1.72-1.76 vd=5355. But the glassforming region of this series is limited to the narrow extent of B 0 being in range of 34-43%. Contrary to the three component glass containing Y O when the content of B 0 is less,i.e. a B 0 content of 34-28%, glass having a rather wide stable region can be obtained. In optical properties too, further high refraction and low dispersion are obtainable in the four component glass of the present invention containing 28.32% of B 0 and these facts are clearly shown by the Table I and FIG. 10.

Referring to the B O -Y O -La O3-ThO four component series of this invention, compositions containing B 0 28%, are glassified when T110 is present in an amount of 27-45%, but, in the region wherein ThO is present in an amount less than this, crystallization is promoted, and in the region wherein Th0 is present in much greater amount the tendency of phase separation becomes worse and the compositions are not glassified. In compositions containing B 0 in an amount of 30%, are glassified when Th0 is present in an amount of 22-48%, and become stable glass when they contain 28% of Y O In compositions containing less Th0 than this, crystallization is promoted and clear glass can not be obtained. In compositions having a much higher ThO content than this, the phenomenon of phase separation becomes violent and homogeneous glass can not be obtained. When the B 0 content is 34%, the ThO content of the stable glass region is decreased to 8-34%, thereby glass cannot be obtained when the T110 content is greater than this. When the content of B 0 is 38%, this tendency becomes remarkable, the amount of Th0; in the stable region becomes 015%. But in any case, the maximum Y O content of the stable region reaches to 23-28%.

In order to stabilize the glass of the four component series, B O -Y O -La O -ThO bivalent metal oxide can be added. Adopting BaO as the most suitable component for extending the glassforming region, without lowering the optical value much, and the glassforming region referred to, the additions of 2%, 4% and 6% of BaO compositions containing B 0 in an amount of 38% are shown in FIGS. 6, 7 and 8 and the weight percent of the compositions of the embodied glass and the optical constant Nd, 2d are shown in Table 2.

It is recognized that when the amount of BaO added is increased, the glassforming region is enlarged very much. But with an increase of the amount of BaO added, Abbes number 11 value increases and the lowering of the refractive index is increased so that addition of BaO over is not desirable and it is preferred to add up to 8% by weight. Referring to the other bivalent metal oxides too, over 10% is not desirable considering the optical properties and it is preferred to include the bivalent metal oxides in the present compositions in a total amount not exceedmg 8 by weight.

TABLE 2 13203 118.203 T1102 YzOa B30 Nd pd 38 15 2 1. 7283 54. 6 38 15 5 2 1. 7337 5d. 4 38 35 10 15 2 1. 7331 54. 3 38 4O 0 20 2 1. 7360 54. 3 38 33 20 5 4 1. 7261 54. 8 38 18 20 20 4 1. 7233 54. 7 38 38 10 1O 4 1. 7283 54. 6 38 48 5 5 4 1. 7341 54. 5 38 43 O 15 4 1. 7344 54. 5 38 36 15 5 6 1. 7283 54. 9 38 26 15 15 6 1. 7243 55. 0 38 11 25 20 6 1. 1753 55. 0 38 6 25 25 6 1. 7151 55. 0

Table 3 shows examples embodying glass containing MgO, CaO, SrO, BaO, CdO, ZnO, A1 0 6e0 ZrO Nb O or Ta O in addition to the four components B O -Y O -La O' -ThO The addition of Ta O ZrO Nb O is very eifective for preventing the tendency toward devitrification even though it has the defect of increasing the dispersion but especially referring to glass having a Nd above 1.75, such an addition is very desirable. But when the content of Ta O ZrO- Nb O is over 10% individually, or

when the sum of two or three components exceeds 15%,

we cannot obtain glass havlng a low d1spers1on WhlCh is the ob ect of this invention.

TABLE 5 Sample Additional No. B203 115 0 T1102 Y1O9 component Nd mi 55 as 10 10 MgO 4 1.7257 54.5 as as 10 10 050 4 1.7325 54.7 as as 10 10 S10 4 1.7321 54.8 as as 10 10 CdO 4 1. 7357 54.5 as as 10 10 ZnO 4 1.7545 53.7 as 40 10 10 A1203 2 1.7504 54.5 as as 10 10 A1203 4 1.7212 54.5 a4 54 20 10 MgO 2 1.7554 53.3 54 a4 20 10 050 2 1.7573 53.8 54 a4 20 1o CdO 2 1.7550 52.4 34 54 20 1o ZnO 2 1.7572 53.1 s4 s4 20 10 B20 2 1.7550 53.5 34 34 20 10 SrO 2 1.7550 53.4 54 a4 20 10 T5205 2 1.7595 52.4 54 34 20 1o N540. 2 1.7528 51.5 34 34 20 10 Z10: 2 1.7515 52.5 34 34 20 10 G004 2 1.7534 53.2 30 20 27 10 T5405 3 1.7519 51.1 30 30 27 10 N520, a 1.7880 49.4 30 a0 27 10 ZrOz a 1.7858 51.5 30 '30 27 1o G502 a 1.7727 52.0 30 30 24 10 T5205 5 1.7552 50.0 30 30 24 10 NbZOll 5 1.7953 47.0 50 so 24 10 Z10; 5 1.7910 50.9 50 30 24 10 0502 5 1. 7555 52.0 30 30 2s 10 a0 2 1.7754 52.3 30 30 2s 10 000 2 1.7503 52.0 50 so 25 10 050 4 1.7804 52.0 50 a0 24 10 CdO 5 1.7801 51.8 30 30 25 10 Z 4 1.7775 51.9

The addition of Ge0 is also effective for preventing the tendency toward devitrification tendency, but using over 10% is not desirable, because the refractive index is lowered without changing the 11 value.

W0 and Ti0 elevate the refractive index, and are effective for preventing devitrification but they increase dispersion, so that their contents must be restricted to a small amount.

S10 and A1 0 serve to prevent devitrification for most of these kinds of glass, even by the addition of a small amount. But when over 5% is added, the optical property is deteriorated and at the same time melting of the raw material becomes difiicult, so that it is not desired.

According to one embodiment of the optical glass of the invention containing the four basic constituents,

a sz a' z b and T1102 in the amounts previously indicated, except that B 0 is present in an amount of 28-40% by weight the glass also contains one or more component selected from Percent by wt. T2 0 0 10 ZrO 0-10 Nb O 0-10 Ge0 0-10 A1 0 0-5 and one or more components in a total amount of up to 8% by weight selected from MgO, CaO, BaO, SrO, ZnO and CdO, as pointed out above. The total amount of the combination of two or more of the components Ta 0 ZrO and Nb O should not exceed 15% by weight.

Alkali metal oxides can be added to the above-described composition containing 2840% B 0 with a resultant improvement in the stability of the glass.

Next, in composition containing B 0 in an amount of 40-42%, as clearly seen from FIG. 5, the glassforming region of the B O -Y O -La O ThO four component series is very narrow. For this series having a reasonable content of B 0 to increase the stability, it is desirable to add 3-10% of a bivalent metal oxide. FIG. 9 shows the glassforming range of compositions 6 containing B in an amount of 41% and also contain Percent by wt. ing 6% of BaO, but it extends extensively towards the B 0 28-42. side having a high content of Th0 and Y O as com- Y 0 224 pared with the series without 36.0. Table 4 shows ex- La O -55 amples embodying the glass containing BaO, CaO, 5 and MgO, SrO, BeO, A1 0 and SiO in addition to B 0 ThO 2-45 m an amount of Yaos Lazoa T1102 glass the amount of Y O being suflicient to render glass more TABLE 4 B107 LazOs Th0; YzO; Additional component Nd ml 41 2a B210 6 1.1094 55.6 41 as 10 5 B110 6 1.7122 55.5 41 43 5 5 B110 6 1.7141 55.5 41 33 5 15 B110 0 1.1133 55.6 41 2s 10 15 S10 6 1.1121 55.6 41 43 5 5 05.0 6 1.7177 55.4 41 4a 5 5 MgO 6 1.1002 55.5 41 2s 10 15 050 6 1.7139 55.5 41 2s 10 15 MgO 6 1.1041 55.1 41 as 5 10 1350,1350 4.2 1.7072 55.2 41 41 5 5 0110,1550, 6,2 1.7094 55,2 41 40 4 5 Ca0,Si0z,Be0 6,3,1 1.6093 56.0

Concerning Ta O ZrO Nb O 6e0 W0 TiO stable against crystallization than the corresponding glass only a small amount of these components may be added not containing Y O to this series having a reasonable amount of B 0 be- 2. An optical glans composition as set forth in claim cause these oxides have a strong tendency to increase 1, in which the component B 0 is in the range 28-40% dispersion. A1 0 SiO and BeO have the effect of preby weight; and further containing at least one comventing devitrification for compositions having a low ponent selected from the group consisting of Ta O content of T1102, but when their contents are over 5%, Zr0 Nb O and 6e0 each in an amount of up to optical properties are deteriorated and melting of the 10% by weight, and A1 0 in an amount up to 5% by raw material becomes difiicult so that it is not desirable. weight, with the proviso that the total amount of Ta O Alkali metal oxides can be added also to the com- 30 ZrO and Nb O does not exceed 15% by weight; position including 4042% B 0 for improving the staand one component in a total amount of up to 8% by bility of the glass. weight selected from the groups consisting of MgO,

Glass having high refraction and low dispersion which CaO, BaO, SrO, ZnO, 010, and mixtures thereof. is composed of the basic glass, B O -Y O -La O -ThO 3. An optical glass composition as set forth in claim four component series of this invention is almost color- 1, in which the component B 0 is included in an amount less or presents only a faint yellow green color and is of -42% by weight; and further containing one comsuperior too in chemical stability, acid resistance and ponent in a total amount of 3-10% by Weight selected weathering resistance. from the group consisting of MgO, CaO, BaO, SrO, and As raw materials, B 0 may be obtained from H BO 40 mixtures thereof; and one component in a total amount BaO and 310 may be obtained from their nitrates, for t l than 5% y weight selected from the group 6011- MgO, CaO, and CdO the carbonate is used; and to obtain slstlng of Beo, 25 2 3, and 'mlXtureS thereofthe other components, the oxides may be used as the glass raw material for preparation and can be produced References cued by using a platinum pot according to the usual manu- 5 UNITED STATES PATENTS fac ri g pr Re. 21,175 8/1939 Morey 106-47 Q Despite the use of some illustrative examples of em- 3,082,101 3/1963 Geifcken et al. 106-47 Q bodiments of the 'invention as described above, it is clear that the present invention is not to be limited to those FOREIGN PATENTS examples of application, but can be variously modified 1,109, 93 4 195 Great Britain 10 47 Q within the scope of the spirit of invention indicated in the patent claims E. Primary Examiner We claim: M. L. BELL, Assistant Examiner 1. An optical glass composition consisting essentially of the components B 0 Y 0 1.21 03 and ThO in a mixture ratio in the range:

US. Cl. XJR. 106-4 7 R 

